Preparation of closures

ABSTRACT

An opening in a tubular member, e.g., a steel tube, is sealed by pressing the walls thereof together while they are at an elevated temperature and in contact with hydrogen. In a preferred embodiment, the steel tube is part of a heat storage vessel, which vessel is filled with or substantially filled with alkali metal hydroxide and in which hydrogen gas is present.

United States Patent 1 3,557,984

[72] Inventor Richard E. Rice 2,637,441 5/1953 Woodman 206/84 Arlington, Mass. 2,791,074 5/ 1957 Woodman 206/84X [21] Appl. No. 659,910 2,177,995 /1939 Ramsaur 29/494 [22] Filed Aug. 11, 1967 2,392,824 1/1946 Lytle et al 29/498X Patented Jan. 26, 1971 2,427,597 9/1947 Garner et al... 29/470.1X [73] Assignee Hooker Chemical Corporation 2,894,323 7/1959 Sowter et a1. 29/497.5X Nlagara Fells, Y k b OTHER REFERENCES z g mgz ew or y mesne Smith, D. P.; Eastwood, L. W.; Garney, D. 1.; Sims, C. E.; g GASES IN METALS, 1953, American Society for Metals,

Cleveland, Ohio, pp. 1 1 1. s4 PREPARATION or CLOSURES Primary Hammer-John F Campbell 4 Claims, 2 Drawing Figs Assistant Examiner-Ronald .1. Shore AttorneysPeter F. Casella, Donald C. Studley, Richard P. U.S. Mueller, James F and j i 29/486, 29/494, 29/497.5, 29/498 [5 1] Int. Cl B23k 31/02 Field of Search 29/481, ABSTRACT: An opening in a tubular member, e.g., a steel tube, is sealed by pressing the walls thereof together while 99/139 they are at an elevated temperature and in contact with hydrogen. in a preferred embodiment, the steel tube is part of [56] References Cted a heat storage vessel, which vessel is filled with or substantially IT STATES PATENTS filled with alkali metal hydroxide and in which hydrogen gas is 2,568,911 9/1951 Cox et a1 29/486X present.

PATENTED JAMES I971 I: 3 n 1.. Q/

PREPARATION OF CLOSURES This invention relates to sealing ofi an opening in a tubular member by heating the member to an elevated temperature at which it may be sealed by the application of pressure, and applying a sealing pressure, while maintaining the surfaces to be sealed together in contact with hydrogen.

The invention is particularly applicable to sealing off heat storage modules or vessels after they are filled with heat storage composition, e.g., alkali metal hydroxide.

A particular advantage of the invention is in the easy effecting of the seal at comparatively low temperatures. Also, the hydrogen gas may be removed from the interior of the sealed member by heating it to a temperature of about700 F. or more, at which temperature the hydrogen will diffuse through the walls of the container, when they are of steel or equivalently behaving metal or material.

In accordance with the present invention, a method of making a seal at an opening in a tube comprises heating said tube in the presence of hydrogen to a sealing temperature and sealing off the tube by application of a sealing force to the heated tube where it is contacted by hydrogen. In a preferred embodiment of the invention, a steel container is filled substantially full of alkali metal hydroxide heat storage composition, a scalable tubular opening in the vessel above the level of the heat storage composition is raised to an elevated temperature and is contacted with hydrogen, being generated in the heat storage composition, and a sealing force is applied to the tube while it is at the elevated temperature and in contact with hydrogen, thus producing a hermetic seal therein, and severing the tube.

Tubes have been sealed in the past by welding, soldering, silver-soldering, brazing compressing and gasketing, However, in the present invention, it has been found that an excellent seal can be made by application of a sealing pressure to a metal tube, such as a steel tube, at a lower elevated temperature than otherwise would be usually employed, if the surfaces of the tube are contacted with hydrogen, preferably as a flowing stream, at the time the seal is made. Although sealing of 'a steel tube, such as one made of mild steel, is a preferred use of the invention, it is also applicable to the sealing of tubes of other metals of construction and to sealing of tubes of other fusible and oxidizable materials. Among the materials to which the present invention may find application are'iron, steels, alloy steels, brass, copper, silver, tin and bronze, to name a few.

Sealing temperatures and pressures are such as are required to make the desired tightseals. These may vary widely but for steel will often be within the range of l,000 F. to l,500 F. and from 1,000 to 200,000 pounds per square inch,although sometimes it may be desirable to use temperatures even higher than l,500 F., even up to the fusion point of the tube. Flow rates of hydrogen may be from 0.1 to 50 or more linear feet per second past the area where the seal is to be effected, and in some cases the hydrogen may be essentially static. In either case, it is important to maintain the hydrogen in contact with the area to be sealed and to avoid the presence of oxidizing agents thereat. This promotes ready sealing and diminishes chance of explosion. Sealing forces may be exerted by rams, clamps, cutting edges, jaws, stamping machines, rollers, punches or presses of various kinds. The forces may be exerted momentarily or over longer periods of time, from as little as onehundredth to 30 seconds but usually less than l second will be required to make a satisfactory seal.

in the preferred application of the invention, to sealing heat storage modules containing sodium hydroxide, the hydrogen employed may be partially or completely generated by the action of iron on the caustic or water in the caustic. A more complete description of the preparation of a preferred waterfree alkali metal hydroxide heat storage composition may be found in application Ser. No. 659,952, entitled Preparation of Heat Storage Composition and Apparatus, filed Aug. 1 1, I967. According to the method described therein, alkali metal hydroxide of 0.05 to l percent moisture content may be made anhydrous by contacting it with dry air or oxygen-free hydrogen for from 10 minutes to24 hours at a temperature of 600 F. to 900 F., after which the composition is preferably treated with iron powder. Then, after the caustic is dehydrated as described, it is filled into a module, having a tubular or equivalently shaped opening, which is sealed according to the present method. Then, by heating the module or vessel toa temperature at which the hydrogen escapes through the walls, it is possible to produce a vessel under vacuum, if it contains only hydrogen and nonvolatile material initially, or one that is under the pressure of the vapor of the contents alone.

The invention will be understood by reference to the ac company drawing, in which:

FIG. 1 is a central vertical sectional view of the top of the module of FIG. 2, before sealing; and

FIG 2 is a partial central vertical sectional view of a sealed alkali metal hydroxide heat storage module.

In FIG. 1 the making of the final seal of the tube of the heat storage module is indicated. Shell 21, of mild steel, is, filled almost full with the caustic being dehydrated by treatment with iron powder, after having been 'dried with oxygen-free hydrogen or dry air. A gas space 35 is left atthe top, usually being from 1 to 10 percent of the shell volume.'End plate 25 has tube 37 attached thereto, as the only connection of the module interior to the outside. Connecting tube 45 is connected to a source of hydrogen which ispassed over the surfaces of the interior of the tube to be sealed while that section of the tube, between a and b, is heated to an elevated temperature between 1,000 F. and l,500 F. and subjected to an impact blow between jaws 39 at a pressure between 5,000 and 100,000 pounds per square inch. The seal so made is a strong one and does not allow air to enter the module. Also, on heating the module, the hydrogen contained therein escapes through the steel walls thereof at a temperature higher than 700 F., preferably about 900 F., leaving the vessel under 'vacuum.

In FIG. 2, the finished sealed heat storage vessel is shown. A steel shell 21 and two end closures 23 and 25, are welded together at 27. The vessel includes internal supporting elements 29 mounted on rod 31, all of mild steel. Heater element 42, of the electric resistor type, is connected to a source of electricity by leads 43. It may be'thermostatically controlled by a thermostat, not shown, in thecaustic. Heat storage medium 33 is alkali metal hydroxide, preferably caustic, free of water and containing some iron powder. Gas 35 is hydrogen which, at high temperature, will pass through steel wall 21. Tube 37 is sealed off at 41 in the manner previously described in discussing HO. 1. l

In operation of the present method, a steel tube'attached as the only opening in a heat storage vessel is heated to l,200 F, hydrogen is brought into contact with the interior of the tube and flowed over the surface thereof at a rate of about 0.3 ft. per second and the tube is sealed off by an impact blow with a force of 50,000 pounds per square inch, which is sufficient to sever the tube. The tube is closed and a seal is made that is airtight. Without the use of the present invention, even at the same temperature and pressure the seal made is not as satisfactory.

The invention has been described with reference to illustrations thereof; however, it is not to be interpreted as limited thereto.

lclaim:

l. A method for hermetically sealing a metallic, tubular opening to a container housing an alkali metal hydroxide heat storage composition which comprises providing an atmosphere of hydrogen in the sealing region of said tube, heat- 4sThe method of claim 3 in which said alkali metal hydroxide heat storage composition contains particulate iron and at least a portion of said hydrogen atmosphere provided in the 

1. A method for hermetically sealing a metallic tubular opening to a container housing an alkali metal hydroxide heat storage composition which comprises providing an atmosphere of hydrogen in the sealing region of said tube, heating said tube to a temperature in the range of 1,000* F. to 1,500* F., applying a sealing force to said tube of from 1,000 to 200,000 pounds per square inch to close and seal said tube and said container, and severing said tube at a point beyond said seal.
 2. The method of claim 1 in which said metallic tube is steel.
 3. The method of claim 1 in which said alkali metal hydroxide heat storage composition contains particulate iron.
 4. The method of claim 3 in which said alkali metal hydroxide heat storage composition contains particulate iron and at least a portion of said hydrogen atmosphere provided in the sealing region of the tubular opening is generated by the reaction of said iron with the alkali metal hydroxide heat storage composition. 